1. Field of the Invention
This invention relates to photographic cameras, and, more particularly, to a shutter arrangement wherein the shutter blades are opened and closed by electromagnetic force.
2. Description of the Prior Art
For the drive source for opening and closing the shutter blades in conventional cameras, use has generally been made of the righting moment of a mechanically tensioned spring. When the film winding operation is performed, the above-identified spring is charged. Then, upon depression of the release button, the shutter is opened. The duration of the exposure time is controlled by a mechanical governor, or a timing circuit, and is terminated by closing the shutter. In any case, the direct drive for the shutter blades relies upon the power mechanically released from the tensioned spring.
It is also known in the art to provide an electromagnetically controlled shutter wherein a tubular coil is arranged in the magnetic field of a permanent magnet upon conduction of current therethrough to effect reciprocating movement by which the shutter blades are opened and closed.
To facilitate incorporation of such electromagnetic actuating device in a narrow space available within the lens mount or barrel accommodating the shutter mechanism, many proposals have been made. These proposals concern the shape and form for minimizing the bulk and size while still preserving the high driving force exerted. To further facilitate minimization of electrical energy consumption by the actuating device, it is desired to transmit motion of the actuating device directly to the shutter drive ring or sector, as the armature of the electromagnetic actuating device is directly connected to the shutter drive ring.
With the foregoing in mind, an object of the present invention is to provide an electromagnetic actuating device for the shutter which overcomes the drawbacks of the conventional actuating device.
Another object of the present invention is to provide an electromagnetic actuating device constructed in the form suited for incorporation in a limited space within the interior of the lens barrel and operable with the limitation of electrical power consumption to a minimum while still preserving the high performance.